Updated June 2020
Generally, there’s no difference between 1080i and 1080p. Both have the same resolution in terms of pixels – 1920 x 1080.
The difference between 1080i and 1080p is in the scan type each uses. 1080i uses interlaced scanning to display pictures while 1080p uses progressive scanning.
You may have heard some television sets being called HD TV and some Full HD TV.
In other words, they are called 1080i and 1080p respectively.
I stands for interlaced and p stands for progressive. Both these types of scanning are explained below.
Although current models are mostly Full HD TV sets, you’ll need to understand the difference between the two especially if you’re thinking about buying an older used set.
Full HD TV is often referred to as a 1080p set and HD as 1080i.
1080p Full HD
1080p means 1080 lines in progressive scanning mode.
This is the kind of scanning that takes place in progressive mode.
The scanning of the lines in each frame takes place from line A to line B. It jumps from A to B straight. Therefore is called progressive.
Compare this with the interlaced mode, as explained below.
1080i means 1080 lines in interlaced scanning mode.
In the interlaced scanning mode, the scanning of the lines in each frame takes place from A1 jumping over to B1 then to A2 before moving to B1 and then jumping to B2. In other words, the lines are scanned alternately.
In progressive video, every single line is a sequence.
In interlaced video alternate lines (A1 + A2) form a sequence.
Frames vs Fields
1080p is frame-based video. In other words, it is referred to in frames per second.
1080i is field-based and is expressed in fields (A1 is a field and A2 is a field) per second.
A field contains half the lines of a frame.
For example for a PAL system TV 1080p will have 25 frames per second. (A + B)
1080i will have 50 fields per second. (A1 + A2+B1+B2)
The interlacing takes place so fast that it’s hardly noticeable to the human eye.
Quality Difference Between 1080i and 1080p
What does this mean in terms of video quality?
Generally you’ll not see much difference between the both. Both have a resolution of 1920 x 1080 pixels (2.1 Megapixels)
However, 1080i will show its shortcomings when it comes to full motion video,
1080i show jitters when subjects in the video move diagonally or vertically.
So, if you’re watching fast moving action you would have a better viewing experience over 1080p.
Also, the bigger your TV screen size the more you’ll see the difference between 1080i and 1080p but this is just a moot point these days as there are hardly any 1080i TV sold these days.
Is 1080i Still Being Used?
In these days of Full HD video, 1080i may seem a little outdated. Still 1080i is being employed for TV broadcas especially among some terrestrial stations while other stations broadcast in 720p.
Is 720p or 1080i Better?
In terms of pixel resolution 1080i boasts 1920 x 1080 whereas 720p is 1280 x 720.
This means 1080i has a horizontal resolution of 1080 lines. But then since it’s interlanced displaying only half of it at each time, the actual horizontal resolution is 1080 divided by 2 which is 540.
720p on the other hand has 720 lines on each frame which is slighter higher than 1080i’s 540 lines. But to the naked eye, the quality difference is negligible.